This application claims priority from Japanese Application No. 357442/2000 filed Nov. 24, 2000.
The present invention relates to an abrasive product which may be in the form of a tape, and more specifically concerns an abrasive tape suitable for finishing processes for magnetic disks, precision apparatuses and precision parts.
When an abrasive product having a flat abrasive layer is used in an abrasive process, it may not be possible to obtain a stable abrasive effect and abrasive precision. This may be because debris (sometimes called xe2x80x9cdetritusxe2x80x9d) from wearing away of the abrasive product and the surface being abraded can be accumulated between the abrasive product and the surface of the article to be abraded, with the result that the surface being abraded may be scratched by the detritus and the detritus may adhere to the surface being abraded and cause degradation in the abrasive precision.
In order to solve this problem, a technique has been known in which convex bodies are formed on the surface of an abrasive product so that detritus particles are collected in the recesses between the bodies and thereby be removed.
For example, a slurry coating liquid, formed by mixing abrasive particles and a bonding agent serving as its binder, is uniformly applied to a surface of a backing film and this is dried and set at a proper temperature to form an abrasive layer. When the abrasive coating liquid is dried and evaporated during the drying and setting process, the solvent is evaporated with convection while the solid components are left, thereby convex bodies (Benard cells) are formed on the surface of the backing.
The spaces between the convex bodies collect detritus particles, thereby removing some of the detritus. However, in the abrasive layer obtained in this manner, shapes of the convex bodies are nonuniform and irregular; therefore, it may not be possible to carry out an abrasive process with high precision.
U.S. Pat. No. 5,147,416 (Ohishi) discloses an abrasive tape whose abrasive layer has a three-dimensional structure. This abrasive tape has a base material, a support layer formed on the base material and an abrasive layer applied on the support layer, and the support layer is formed to have uniform, regular convex surface portions. However, since the support layer is formed by molding and curing a liquid composition, unwanted deformations may occur due to contraction at the time of curing, making it difficult to provide uniform, regular convex surface portions. Moreover, the molded product of this type is susceptible to cracking due to a frictional force at the time of abrading, making it difficult to maintain uniform, regular convex surface portions during the abrasive process.
Japanese Laid-Open Patent Publication No. 63-16980 (Yamaguchi et al.) discloses an abrasive tape having an abrasive layer on the surface which include concavoconvex surface portions. A binder and abrasive grains are applied onto a film backing and, after having been dried, this is subjected to an embossing process by a roll having a concavoconvex pattern, and then subjected to a pressing process by using a calendar roll with a concavoconvex printing plate cylinder. The concavoconvex pattern thus formed is comparatively uniform and regular, which makes it possible to carry out an abrasive process with high precision. Moreover, this product has high strength, is superior in the shape-retaining stability, and also has high cleaning effect. However, these concavoconvex portions are formed by pressing the surface of the abrasive layer using a roll. For this reason, the longer dimension of the abrasive grains are deployed parallel with the surface of the abrasive layer, and embedded therein, making the abrasive tape inferior in the abrasive performance. Moreover, it is difficult to apply the abrasive grains to the thin layer, and this method is inferior in the retaining force of the abrasive grains in use.
U.S. Pat. No. 5,015,266 (Yamamoto) discloses an abrasive tape in which a backing film having a concavoconvex pattern preliminarily formed by an embossing process is provided with abrasive grains bonded onto the surface thereof by a binder. However, in this abrasive tape, the coating method of the binder and the abrasive grain is by a slurry coating method, such as roll coating method, knife coating method, die coating method and reverse coating method. Therefore, in the same manner as described above, the longer dimension of the abrasive grains are deployed parallel with the surface of the abrasive layer, and embedded therein, making the abrasive tape inferior in the abrasive performance. Moreover, it is difficult to apply the abrasive grains to the thin layer, and this method is inferior in the retaining force of the abrasive grains in use.
Japanese Laid-Open Patent Publication No. 2001-113467 (Okawa et al.) discloses an abrasive tape in which a backing film having a concavoconvex pattern is provided with layer of binder and abrasive grains having a corresponding concavoconvex surface. However, in this abrasive tape, the coating method of the binder and the abrasive grain slurry is by roll coating. Furthermore, the abrasive coating comprises multiple layers of abrasive grains randomly embedded therein having a particle size between 0.1-0.8 xcexcm. Therefore, the bulk of the abrasive grains are not deployed in an erect orientation with respect to the film plane, resulting in an abrasive tape having inferior abrasive performance.
The present invention has been devised to solve the above-mentioned conventional problems, and its objective is to provide an abrasive tape whose abrasive layer has a concavoconvex pattern that is superior in the uniformity, regularity and shape-retaining stability, and which is superior in the cleaning effect, abrasive precision, abrasive force and efficiency in using the abrasive grains.
The present invention in one aspect, provides an abrasive product comprising:
a. a sheet-like backing including a plurality of concavoconvex portions, said backing having a first major surface including convex portions and an opposite second major surface including concave portions opposite said convex portions;
b. a coating of a binder applied over the first major surface and the convex portions; and
c. a single layer of a plurality of substantially erectly oriented abrasive particles bonded to the backing by the binder coating.
In a further aspect, the present invention provides a method of making an abrasive product comprising:
a. providing a sheet-like backing including a plurality of concavoconvex portions, said backing having a first major surface including convex portions and an opposite second major surface including concave portions opposite said convex portions;
b. coating the first major surface of the backing with an uncured composition which is curable to provide a binder,
c. applying abrasive particles to the uncured composition coating with an electrostatic sprayer; and
d. curing the uncured composition to provide the binder coating.
The term xe2x80x9cconcavoconvex portionsxe2x80x9d refers to portions of the backing which have been treated to have an other than flat surface having a plurality of convex portions on one surface, each of which has an opposite concave portion on the other surface.
The term xe2x80x9cerectly orientedxe2x80x9d refers to a characteristic in which the longer dimensions of at least some of the abrasive particles are oriented substantially perpendicular to the backing of the abrasive material. This allows at least a portion of the abrasive grains to protrude from the outermost surface of the abrasive layer.